21516171 has 8 divisors (see below), whose sum is σ = 28741440. Its totient is φ = 14317512.

The previous prime is 21516167. The next prime is 21516181. The reversal of 21516171 is 17161512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21516171 - 2² = 21516167 is a prime.

It is a super-2 number, since 2×21516171² = 925891229002482, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21516161) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4681 + ... + 8058.

It is an arithmetic number, because the mean of its divisors is an integer number (3592680).

Almost surely, 2^21516171 is an apocalyptic number.

21516171 is a deficient number, since it is larger than the sum of its proper divisors (7225269).

21516171 is a wasteful number, since it uses less digits than its factorization.

21516171 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13305.

The product of its digits is 420, while the sum is 24.

The square root of 21516171 is about 4638.5526837582. The cubic root of 21516171 is about 278.1345853869.

Adding to 21516171 its reverse (17161512), we get a palindrome (38677683).

The spelling of 21516171 in words is "twenty-one million, five hundred sixteen thousand, one hundred seventy-one".